1. Field of the Invention
This invention relates to fence tensioners especially designed for use with flexible polymer fence rails.
2. Background of the Invention
Over the past several years, composite metal and plastic fence systems have become increasingly accepted for the confinement of livestock, thoroughbred horses and the like. Typically, the fence rails are comprised of at least two wires or other high strength fibers encased in a polymer such as vinyl or other suitable plastic web. Depending on the width of the fence rail, two wires may extend along the opposite edges of the slat or, for wider slats, a third or even fourth wire may be added intermediate the edge wires. To maximize the effectiveness of the flexible fence rails, tensioning devices must be utilized to insure that the individual rails do not sag between posts. Fence tensioners have long been used to tighten individual strands in wire fence systems. The forces that need to be applied to the fence systems are such that the fence tensioners are typically constructed of metal, which is often at least partially electrically conductive. Examples of fence tensioners can be found in U.S. Pat. Nos. 6,431,487; 6,648,305; 6,848,678; and 7,475,869.
It is known to include electrically conductive wires in fence constructions for the confinement of livestock. Such systems generally include one or more electrically conductive wires. It is also known to utilize an electrically conductive wire in combination with a more visible horizontal structural element to enhance the likelihood that the animal, when shocked, will shy away from the fence. A particularly useful and more visible horizontal structural element is known to have a plurality of vertically spaced, high tensile-strength wires joined by intervening plastic webs. Examples of electrically conductive fence wires with high visibility plastic webbing can be found in U.S. Pat. Nos. 4,755,633; 5,203,542; and 6,834,846. Commonly employed fence tensioners are sometimes not electrically isolated from the conductive portion of the fence rail, thus contributing to a shorting or ground fault that can cause some portion of an electrical fence to become ineffective or inoperative.
There remains a need for a fence tensioner that will contribute to the electrical isolation of the charge carrying wires of a fence rail.